I think I know what is going on here. You are feeling a little bit of self doubt. If other people tell you you are a good singer and they are your friends or family then they are not likely to be lying to you.
It is not important to be the worlds best singer but it is important to do what you love and if singing and song writing are something you love and are good at then you should keep your head high!
Not writing songs every day is not a bad thing, sometimes we need time to take a creative break and re charge our batteries and sometimes we just need to wait for the right inspiration. So when your friend asks you if you have "written any songs lately" you can hold your head up and tell her the the truth, you have nothing to be ashamed of!
"Sing like no one is listening" and "Write even if you think no one will like it!"
Keep your head up and sing when you feel moved to!